Put a cork on it: The comeback of this versatile building material continues

Albert Rooks' house
CC BY 2.0 Albert Rook's house covered in cork/ Lloyd Alter

The cork industry is no longer in crisis as demand increases for this greenest of materials.

We have long been fans of cork at TreeHugger, and have shown it being used in everything from tiles to wallets and even bathing suits. But most importantly, it is a terrific building material. Albert of Small Planet Building Supply, who covered his house in Olympia, Washington, described how easy it is to use:

Working with cork doesn't leave you itching and scratching. It doesn't leave the job site covered in foam particles. There are no endocrine damaging fire retardants. It doesn't compress like mineral wool so there are no tedious screws to move in or out to keep a wall plane straight. It comes in packs that are easy to lift and carry, and panels that are easy to apply and can be nailed in place with a nail gun.

Now Blaine Brownell, the materials expert at Architect Magazine, picks up the story of cork, describing how a decade ago, cork was in crisis.

Though the material had been used in wine bottles for centuries, the Portuguese cork industry—which supplies most of its raw material for use in wine bottles—was facing stiff competition from manufacturers of plastic and metal screw-caps, which were gaining in popularity due to increasing instances of “corked” bottles.

Iberian LynxIberian Lynx/CC BY 2.0

They were also losing their trees to real estate development, jobs in cork were being lost and the cute little Iberian Lynx was losing its habitat. Brownell notes that the industry reinvented itself, and describes the reasons that it has become such a popular and green architectural material:

Cork oak trees are not cut down to harvest the material; rather, their bark is stripped every nine years. Additionally, the trees that comprise more than 5 million acres of cork forest globally can live up to three centuries. Like other cellulosic materials, cork stores carbon. Conservative estimates by researchers at Netherlands-based environmental consultancy CE Delft suggest that between 0.95 and 1.25 metric tons of carbon are sequestered per metric ton of harvested raw cork, and, like timber, this carbon remains trapped within the material until it is destroyed. Considering that discarded cork is routinely recycled into new products, it makes for an ideal carbon bank.

A wall of corkA wall of cork at Small Planet Building Supplies: It doesn't weigh much but it takes up space/CC BY 2.0

Whenever we write about cork, readers complain about the transatlantic shipping, and Brownell mentions it as well. Alex Wilson of BuildingGreen agonized over this when he insulated his house with the stuff, but in the end concluded that the virtues outweighed the distance. It is not like the stuff is air-freighted, and look at the advantages: a traditional craft is maintained, a natural habitat is preserved, and it is a renewable, sustainable material that can be used as insulation, cladding or flooring. It is fire resistant and totally natural. Outside of the shipping, it has a positive carbon footprint; it is hard to imagine anything greener, unless it is recycled cork. Alex exclaimed:

It contains nothing but cork—nothing! As it is produced today by Amorim Isolamentos, S.A., the granules are poured into large vats and heated with steam in an autoclave at about 650°F for 20 minutes. The heat expands the granules by about 30% and releases a natural binder, suberin, that exists in the cork. There are no added ingredients.

Fortunately, people are catching on to this; Brownell concludes by quoting the head of the Cork Association: “We are living in a historic moment for cork. We have a new confidence, and we see a changing perception of the cork industry.”

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